RV Electricity – Tighten those transfer switch terminals carefully

By Mike Sokol 

Dear Mike,
Saw your seminar in Goshen at the Heartland Rally, and it was really informative. Can you go into more detail on how to properly tighten the terminal screws in a generator transfer switch without breaking them off? Thanks. —Billy D

Dear Billy,
Certainly. First I’ll do a little overview of why these screws always seem to work loose, and go over the tightening procedure. I’ll include a video from my Advanced RV Electricity Seminar I did in Funkstown, MD, on June 8th.

First of all, I’m a firm believer that most overheated wiring situations in transfer switches are due to loose screws in the terminal connections on the contactor/relays. This is simply due to road vibration and heating/cooling cycles, none of which these electrical components would normally experience in a home wiring situation.

So what are we to do? Well, start with a yearly maintenance schedule where you re-torque all the wiring terminals in your transfer switch, inverter/converter connection and circuit breakers. It’s also a good idea to test the screws in your RV’s shore power inlet, as well as inspecting everything for any signs of overheating or physical damage.

Now, as I hinted at in my RVelectricity seminar, you don’t want to simply get wrenching down on these wiring terminals as it’s pretty easy to break off the insulating tab. What you need to do is determine the actual in/lbs of torque recommended by the manufacturer. Note that I said INCH/POUNDS not FOOT/POUNDS. You torque lug nuts on your wheels to maybe 75 to 125 ft/lbs, but electrical terminals on relays and inverters are typically more like 25 or 35 INCH/LBS.

I’m a big believer in using the right tool for the job, so a variable torque screwdriver that “breaks” at the desired torque (not just clicks) is what’s needed. Here’s what I used in my video, which is a little too expensive for casual users but not too much for a professional RV technician or shop.

First of all, before you start sticking metal objects in anything with wire, make sure all power is off. That is, your RV needs to be disconnected from shore power, generator power and inverter power.

Next, determine the proper amount of torque needed for each terminal connection. On the Southwire transfer switch I’m showing, the screw terminals require 35 in/lbs of torque. So set your screwdriver to the proper amount of twisting action as specified.

Now back the screw out a quarter turn to make sure it’s free of any rust or spalling that would lock up a loose screw.

Proceed to tighten the screw normally until the torque limiting screwdriver “clicks” and breaks at the correct amount of torque. “Rinse and repeat” until you’ve covered all of the screws in the panel.

While you’re at it, carefully inspect all wiring and connectors for any signs of damage, either due to the insulation being overheated or cut, or wiring strands hanging out of the screw terminal.

BTW: Here’s the less expensive version of my commercial duty torque screwdriver that should work just fine for your terminal tightening jobs. You can purchase it on Amazon HERE.

That’s it. You’ve eliminated a lot of potential failure points during your next trip so you can enjoy more camping time with friends and family. Plus, you’ve increased the safety of your RV’s electrical system, which is most important of all.

More on this later, but in the meantime – let’s play safe out there….

Mike Sokol is an electrical and professional sound expert with 40+ years in the industry. His excellent book RV Electrical Safety is available at Amazon.com. For more info on Mike’s qualifications as an electrical expert, click here.

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